11 66 521 Checking function of vacuum system (N20)

Special tools required:

81 31 2 357 800 (previously: 81 38 2 201 924)

Attention!

Note the sequence of the diagnosis instructions in the ISID :

Depending on the fault pattern, the order of operations in the repair instructions may be different from the order of operations in the ISID .

Carry out procedure to check the vacuum system.

Check suction effect of vacuum pump .

Detach vacuum line (1) from vacuum reservoir.

Detach vacuum line (2) from exhaust flap.

Fig 1: Identifying Vacuum Lines

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Check suction effect of vacuum pump .

Fit special tool 81 31 2 357 800 (previously: 81 38 2 201 924).

Seal vacuum line from vacuum pump to vacuum reservoir with a suitable plug (1).

Follow diagnosis instruction.

Fig 2: Checking Vacuum Pump Suction

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Check vacuum reservoir .

Reconnect vacuum line from vacuum pump to the vacuum reservoir.

NOTE: When used with the IMIB the absolute pressure is displayed.

Follow diagnosis instruction.

Fig 3: Checking Vacuum Reservoir With IMIB

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Check vacuum reservoir .

Detach vacuum line (1) from vacuum reservoir.

Seal connection on vacuum reservoir with sealing cap (2).

Follow diagnosis instruction.

Fig 4: Identifying Vacuum Line And Sealing Cap

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Functional check of exhaust flaps .

Check function of exhaust flap (1) on both rear silencers (2).

Follow diagnosis instruction.

Fig 5: Identifying Exhaust Flap

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Check suction operation on the exhaust flap .

Disconnect vacuum line (1) to exhaust flap at left spring strut dome and reconnect with a T-piece.

Connect special tool 81 31 2 357 800 (previously: 81 38 2 201 924) with T-piece.

NOTE: When used with the IMIB the absolute pressure is displayed.

Fig 6: Connecting Special Tool (2 201 924) With T-Piece

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Follow diagnosis instruction.

Leakage test of hoses to exhaust flaps .

Check leakage test of hoses to exhaust flaps.

Disconnect vacuum line with pliers (1) as shown in the illustration.

Follow diagnosis instruction.

Fig 7: Disconnecting Vacuum Line With Pliers

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Pressure converter connections

Disconnect vacuum hose at connection (VAC = vacuum reservoir).

Disconnect vacuum hose at connection (OUT= turbocharger vacuum unit).

Fig 8: Identifying VAC And OUT Vacuum Hose Connections

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Leakage test of hoses to wastegate valve .

Connect vacuum line (1) with vacuum line (2) from vacuum reservoir with a T-piece and special tool 81 31 2 357 800 (previously: 81 38 2 201 924).

Follow diagnosis instruction.

Fig 9: Connecting Vacuum Lines With T-Piece And Special Tool (2 201 924)

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Check function of wastegate capsule .

Check function of linkage.

Follow diagnosis instruction.

Fig 10: Checking Function Of Wastegate Capsule

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NOTE: Remove all special tools.
Reassemble the vehicle.